1. Field of the Invention
The present invention relates to non-aging, impact-modified polycarbonate compositions and moulding compositions which are distinguished by an improved balance of multiaxial low-temperature impact strength and flowability, good dyeability and a high heat distortion resistance.
2. Description of Related Art
Compositions comprising polycarbonate, graft polymer based on rubbery-elastic, non-aging graft base and vinyl aromatic copolymer are known in principle.
DE-A 4434965, for example, discloses such compositions that have an improved balance of low-temperature strength, rigidity and flow behaviour and that comprise polycarbonate (A), graft polymer with rubbery-elastic graft bases having a specific particle size (B) and thermoplastic vinyl aromatic (co)polymer (C), wherein the relative proportions B to C are limited. Silicone-acrylate composite rubbers are not disclosed as the rubbery-elastic graft base in this application.
EP-A 0537014 discloses compositions having improved low-temperature strength that comprise a thermoplastic resin, for example a polycarbonate, a vinyl polymer or a mixture thereof, and an impact-modifying amount of a specific multiphase graft polymer based on polyorganosiloxane/polyvinyl. Compositions comprising polycarbonate, vinyl polymer and graft polymer in which the vinyl polymer and the graft polymer are used in specific relative proportions are not disclosed.
EP-A 0486853 discloses compositions having improved dyeability through the use of pigments comprising a specific graft polymer based on a polyorganosiloxane-polyalkyl (meth)acrylate compound rubber and optionally further thermoplastics such as, for example, polycarbonate.
EP-A 0430134 discloses compositions that have excellent impact strength, surface hardness and surface quality and that comprise polycarbonate and a specific polyorganosiloxane graft polymer based on a composite rubber as graft base, which comprises from 1 to 10 wt. % polyorganosiloxane rubber and from 99 to 90 wt. % polyalkyl (meth)acrylate rubber in non-separable form. It is disclosed that the compositions can additionally also contain homopolymers or copolymers based on vinyl monomers. There is no mention in this application of particular advantages that can be achieved in terms of properties when the three components are used in the specific mixing ratio.
EP-A 0307963 discloses compositions that have good resistance to chemicals, to weathering and to heat as well as good impact strength and that comprise polycarbonate, graft polymer based on a silicone-butyl acrylate composite rubber base and vinyl copolymer. However, the disclosed compositions exhibit a disadvantageous ratio of graft polymer content to vinyl copolymer content. The dyeing of such compositions in dark and brilliant colours requires large amounts of pigments, which result in a deterioration of the mechanical properties of the composition.
EP-A 1334153 discloses compositions that have improved stability to heat aging, a high surface quality and good processability and that comprise polycarbonate, graft polymer based on silicone-acrylate composite rubber, vinyl copolymer and mineral filler (glass fibres). These compositions have a strength that is inadequate for many applications—in particular at low temperatures.